The kernel function tracer, Ftrace, evolved from work done by Steven Rostedt, and many others, as they were tracking down the causes of high scheduling latency in real-time applications. Ftrace appeared in Linux 2.6.27 and has been actively developed since then. There are a number of documents describing kernel tracing in the kernel source in Documentation/trace.
Ftrace consists of a number of tracers that can log various types of activity in the kernel. Here, I am going to talk about the function and function_graph tracers and about the event tracepoints. In Chapter 16, Real-Time Programming, I will revisit Ftrace and use it to show real-time latencies.
The function tracer instruments each kernel function so that calls can be recorded and timestamped. As a matter of interest, it compiles the kernel with the -pg switch to inject the instrumentation, but the...
